A wireless network may include channels with different bandwidths. Packets transmitted on channels with different bandwidths may have different preambles. For example, the proposed IEEE 802.11ah (“802.11ah”) WiFi standard includes channels with bandwidths of 1, 2, 4, 8, and 16 MHz. The 1 MHz packets have different preambles than the 2, 4, 8, and 16 MHz packets. The use of different preambles complicates packet detection: packet detection should be performed reliably without prior knowledge of the packet bandwidth.